In addition to the standard evaporator outlet 0-ring P/N 3053204 .549" ID, there is a thicker outlet 0-ring P/N 3090774 3/4" available through GMPD. This thicker 0-ring may be used on the evaporator outlet fitting in cases where the standard 0-ring does not provide a sufficient seal. Either of the outlet 0-rings may be used in conjunction with the inlet 0-ring P/N 3053203 .364" ID at the evaporator block fitting.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.